Hi,
With external processes or helpers participating to the VM support, it
becomes necessary to handle their migration. Various options exist to
transfer their state:
1) as the VM memory, RAM or devices (we could say that's how
vhost-user devices can be handled today, they are expected to
restore from ring state)
2) other "vmstate" (as with TPM emulator state blobs)
3) left to be handled by management layer
1) is not practical, since an external processes may legitimatelly
need arbitrary state date to back a device or a service, or may not
even have an associated device.
2) needs ad-hoc code for each helper, but is simple and working
3) is complicated for management layer, QEMU has the migration timing
The proposed "dbus-vmstate" object will connect to a given D-Bus
address, and save/load from org.qemu.VMState1 owners on migration.
Thus helpers can easily have their state migrated with QEMU, without
implementing ad-hoc support (such as done for TPM emulation)
D-Bus is ubiquitous on Linux (it is systemd IPC), and can be made to
work on various other OSes. There are several implementations and good
bindings for various languages. (the tests/dbus-vmstate-test.c is a
good example of how simple the implementation of services can be, even
in C)
dbus-vmstate is put into use by the libvirt series "[PATCH 00/23] Use
a slirp helper process".
v2:
- fix build with broken mingw-glib
-----BEGIN PGP SIGNATURE-----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=M4kD
-----END PGP SIGNATURE-----
Merge remote-tracking branch 'remotes/elmarco/tags/dbus-vmstate7-pull-request' into staging
Add dbus-vmstate
Hi,
With external processes or helpers participating to the VM support, it
becomes necessary to handle their migration. Various options exist to
transfer their state:
1) as the VM memory, RAM or devices (we could say that's how
vhost-user devices can be handled today, they are expected to
restore from ring state)
2) other "vmstate" (as with TPM emulator state blobs)
3) left to be handled by management layer
1) is not practical, since an external processes may legitimatelly
need arbitrary state date to back a device or a service, or may not
even have an associated device.
2) needs ad-hoc code for each helper, but is simple and working
3) is complicated for management layer, QEMU has the migration timing
The proposed "dbus-vmstate" object will connect to a given D-Bus
address, and save/load from org.qemu.VMState1 owners on migration.
Thus helpers can easily have their state migrated with QEMU, without
implementing ad-hoc support (such as done for TPM emulation)
D-Bus is ubiquitous on Linux (it is systemd IPC), and can be made to
work on various other OSes. There are several implementations and good
bindings for various languages. (the tests/dbus-vmstate-test.c is a
good example of how simple the implementation of services can be, even
in C)
dbus-vmstate is put into use by the libvirt series "[PATCH 00/23] Use
a slirp helper process".
v2:
- fix build with broken mingw-glib
# gpg: Signature made Mon 06 Jan 2020 14:43:35 GMT
# gpg: using RSA key 87A9BD933F87C606D276F62DDAE8E10975969CE5
# gpg: issuer "marcandre.lureau@redhat.com"
# gpg: Good signature from "Marc-André Lureau <marcandre.lureau@redhat.com>" [full]
# gpg: aka "Marc-André Lureau <marcandre.lureau@gmail.com>" [full]
# Primary key fingerprint: 87A9 BD93 3F87 C606 D276 F62D DAE8 E109 7596 9CE5
* remotes/elmarco/tags/dbus-vmstate7-pull-request:
tests: add dbus-vmstate-test
tests: add migration-helpers unit
dockerfiles: add dbus-daemon to some of latest distributions
configure: add GDBUS_CODEGEN
Add dbus-vmstate object
util: add dbus helper unit
docs: start a document to describe D-Bus usage
vmstate: replace DeviceState with VMStateIf
vmstate: add qom interface to get id
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
c4d1069c25